Current xerographic printing machines use charging devices in the charging, recharging, pre-transfer, transfer, de-tack and pre-clean stations. Charging devices comprise several types, including glass-coated alternating-current wire scorotrons, also known as discorotrons, and solid-state devices, also known as "microtrons".
These two devices, discorotrons and solid-state chargers, each provide substantially different operating characteristics. For example, while the operating-life of a discorotron is substantial, the discorotron generates a substantial amount of undesirable gaseous emissions such as, for example, ozone. In contrast, while a solid-state charger has a relatively short life, the solid-state charger produces only a fraction of the ozone of the equivalent discorotron. For example, in a preliminary experiment, a solid-state charger emitted only about one-seventh (1/7) of the ozone emitted by the equivalent discorotron.
What is needed, therefore, is an improved charging apparatus that generates acceptable amounts of undesirable ozone gas while still providing a satisfactory operating life.